Substituted Cyanophosphine Additives for Lithium Conducting Carbon Phosphonitrides

ABSTRACT

Cyanophosphines other than P(CN) 3  react with lithium dicyanamide to produce lithiated carbon phosphonitrides with mobile Li +  ions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application claims the benefit of U.S. Provisional PatentApplication Ser. No. 63/286,355 filed on Dec. 6, 2021, the entirety ofwhich is incorporated herein by reference, and is related to U.S. Pat.Nos. 10,510,458 and 9,409,936.

FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

The United States Government has ownership rights in this invention.Licensing inquiries may be directed to Office of Technology Transfer, USNaval Research Laboratory, Code 1004, Washington, D.C. 20375, USA;+1.202.767.7230; techtran@nrl.navy.mil, referencing NC 210918.

BACKGROUND

Lithium ion conducting carbon phosphonitride polyelectrolytes weredocumented in U.S. Pat. No. 10,510,458 and in “A solid, amorphous,lithiated carbon phosphonitride displaying lithium ion conductivity,” A.P. Purdy et al. J. Solid State Chem. 2022, 305, 122649. As non-flammablematerials produced by the reaction of lithium dicyanamide (LiN(CN)₂)with phosphorus tricyanide (P(CN)₃) in mutual solvents, they exhibitpotential for replacing the highly flammable separator materials inlithium ion batteries that make these batteries dangerous and prone tocombustion. These lithium-containing carbon phosphonitrides arestructurally similar to and derived from similar materials as C₃N₃P, astoichiometric carbon phosphonitride described in U.S. Pat. No.9,409,936 B2 (6 Aug. 2015) and article “P(CN)₃ Precursor for CarbonPhosphonitride Extended Solids,” B. L. Chaloux et al. Chem. Mater. 2015,27(13), 4507.

A need exists for new lithium-containing carbon phosphonitrides as wellas methods for the preparation thereof.

BRIEF SUMMARY

In a first embodiment, a method of preparing lithiated carbonphosphonitride material comprises reacting LiN(CN)₂ with a derivatizedcyanophosphine, optionally not tricyanophosphine.

Another embodiment is a lithiated carbon phosphonitride material in astate of having been made by a method of the first embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary method for preparing lithiated carbonphosphonitride material by reacting LiN(CN)2 with(diphenylamino)dicyanophosphine in γ-valerolactone.

DETAILED DESCRIPTION Definitions

Before describing the present invention in detail, it is to beunderstood that the terminology used in the specification is for thepurpose of describing particular embodiments, and is not necessarilyintended to be limiting. Although many methods, structures and materialssimilar, modified, or equivalent to those described herein can be usedin the practice of the present invention without undue experimentation,the preferred methods, structures and materials are described herein. Indescribing and claiming the present invention, the following terminologywill be used in accordance with the definitions set out below.

As used herein, the singular forms “a”, “an,” and “the” do not precludeplural referents, unless the content clearly dictates otherwise.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items.

As used herein, the term “about” when used in conjunction with a statednumerical value or range denotes somewhat more or somewhat less than thestated value or range, to within a range of ±10% of that stated.

Overview

As described herein, lithiated carbon phosphonitride materials,previously described in U.S. Pat. No. 10,510,458, can be produced notonly from the reaction of lithium dicyanamide (LiN(CN)₂) withtricyanophosphine (P(CN)₃), but from the reaction of LiN(CN)₂ with anyother derivatized cyanophosphine. Cyanophosphines are defined herein asphosphorus compounds bearing one or more cyano/nitrile (CN) substituents(i.e. P-CN) with organic substituents comprising the remainder offunctional groups on phosphorus (e.g. R_(3-x)P(CN)_(x) where x is 1, 2,or 3).

In various aspects, lithiated carbon phosphonitrides so produced arefree of, or nearly free of, elements other than carbon, phosphorus,nitrogen, and lithium. Such contaminants might be present at less than5%, 4%, 3%, 2%, or 1% by mass.

Example

In a nitrogen filled drybox, a stock solution of lithium dicyanamide wasprepared by dissolving 10 mmol (0.730 g) LiN(CN)₂ in 9.7 mmol (1.165 g)anhydrous sulfolane and 83.4 mmol (8.350 g) anhydrous γ-valerolactone.Three NMR-scale reactions (A, B, and C) were prepared from this stocksolution by dissolving (diphenylamino)dicyanophosphine (Ph₂NP(CN)₂) atvarying molar ratios in 0.5 gram aliquots of stock solution. “A” wasprepared by dissolving 40.9 mg (0.163 mmol) Ph₂NP(CN)₂ in 0.5 gramsstock solution (3:1 LiN(CN)₂ to cyanophosphine molar ratio); “B” wasprepared by dissolving 61.3 mg (0.244 mmol) Ph₂NP(CN)₂ in 0.5 gramsstock solution (2:1 LiN(CN)₂ to cyanophosphine molar ratio); and “C” wasprepared by dissolving 122.6 mg (0.488 mmol) Ph₂NP(CN)₂ in 0.5 gramsstock solution (1:1 LiN(CN)₂ to cyanophosphine molar ratio).

The NMR tubes were flame sealed under vacuum and ¹H, ⁷Li, and ¹³C NMRspectra acquired in the absence of heating. The three samples weresubsequently heated to 100° C. for 2 hours in a water bath, after whichthe viscosity of each solution increased substantially and the colordarkened from red to almost black. NMR spectra were subsequentlyacquired on these materials, from which speciation before and afterheating was assessed.

All reactions showed significant consumption of the dicyanamide anion,with the highest molar ratio (reaction “C”, 1:1 LiN(CN)₂ to Ph₂NP(CN)₂)being most viscous and showing only 10% of the initial dicyanamidecontent remaining after 2 hours at 100° C. Likewise, Ph₂NP(CN)₂ isconsumed over the course of reaction in each of the three samples, withreaction “C” exhibiting only 70% of the initial Ph₂NP(CN)₂ content afterheating for 2 hours. Despite the consumption of both dicyanamide andcyanophosphine, ⁷Li diffusion ordered NMR spectra (DOSY) show that Lidiffuses faster, on average, post-reaction than pre-reaction,demonstrating that Li⁺ remains a mobile species despite theoligomerization of starting materials.

Further Embodiments

Solvents may comprise any polar aprotic liquids that exhibit mutualsolubility for lithium dicyanamide and cyanophosphine, and are thereforenot limited to γ-valerolactone and sulfolane (as described in theexample) or acetonitrile, dimethoxyethane, and pyridine (as described inU.S. Pat. No. 10,510,458). Likewise, cyanophosphine reagents are notlimited to P(CN)₃ and Ph₂NP(CN)₂, but may additionally comprise anymono- or dicyanophosphine substituted with an organic substituent.(Diphenylamino)dicyanophosphine was chosen as an example due to its easeof synthesis and solubility in a variety of solvents.

Utilizing (diphenylamino)dicyanophosphine (Ph₂NP(CN)₂) as a reagent toproduce lithiated carbon phosphonitrides is an alternative to the use ofphosphorus tricyanide (P(CN)₃) as described in U.S. Pat. No. 10,510,458.Reaction of these two materials with lithium dicyanamide (LiN(CN)₂) isthe only currently known way of making lithiated carbon phosphonitride.The properties of lithiated carbon phosphonitride made with differentreagents may vary based on the chosen cyanophosphine reagents, but thesematerials should be considered related compounds

Advantages

This is believed to be the first example of cyanophosphines other thanP(CN)₃ reacting with lithium dicyanamide to produce lithiated carbonphosphonitrides with mobile Li⁺ ions. This technology significantlyexpands the range of precursors that can be used to prepare lithiatedcarbon phosphonitride, with implications for modifying criticalmaterials properties, including mechanical strength, glass transitiontemperature, and electrochemical stability.

Concluding Remarks

All documents mentioned herein are hereby incorporated by reference forthe purpose of disclosing and describing the particular materials andmethodologies for which the document was cited.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without departing from the spiritand scope of the invention. Terminology used herein should not beconstrued as being “means-plus-function” language unless the term“means” is expressly used in association therewith.

What is claimed is:
 1. A method of preparing lithiated carbonphosphonitride material, the method comprising reacting LiN(CN)₂ with aderivatized cyanophosphine.
 2. The method of claim 1, wherein saidderivatized cyanophosphine is not tricyanophosphine.
 3. The method ofclaim 1, wherein said derivatized cyanophosphine is(diphenylamino)dicyanophosphine.
 4. A method of preparing lithiatedcarbon phosphonitride material, the method comprising reacting LiN(CN)₂with (diphenylamino)dicyanophosphine in γ-valerolactone.
 5. A lithiatedcarbon phosphonitride material in a state of having been prepared byreacting LiN(CN)₂ with a derivatized cyanophosphine.